Modulations in Spectra of Galactic Gamma-ray sources as a result of photon-ALPs mixing

TL;DR

This paper investigates how photon-ALPs mixing can cause energy-dependent modulations in the spectra of galactic gamma-ray sources, using eight years of Fermi data to search for signatures of ALPs.

Contribution

It provides a novel analysis of gamma-ray spectral modulations due to photon-ALPs mixing using extensive observational data and galactic magnetic field models.

Findings

Constraints on photon-ALPs coupling constant and ALPs mass.

Evidence of spectral modulations consistent with photon-ALPs mixing.

Assessment of photon survival probability in the Galactic plane.

Abstract

Axion like particles (ALPs) are fundamental pseudo scalar particles with properties similar to Axions which are a well-known extension of the standard model to solve the strong CP problem in Quantum Chromodynamics. ALPs can oscillate into photons and vice versa in the presence of an external tranversal magnetic field. This oscillation of photon and ALPs could have important implications for astronomical observations, i.e. a characteristic energy dependent attenuation in Gamma ray spectra for astrophysical sources. Here we have revisited the opportunity to search Photon-ALPs coupling in the disappearance channel. We use eight years of Fermi Pass 8 data of a selection of promising galactic Gamma-ray source candidates and study the modulation in the spectra in accordance with Photon-ALPs mixing and estimate best fit values of the parameters i.e. Photon-ALPs coupling constant$ (g_{\alpha\gamma\gamma} )$ and ALPs mass($m_{\alpha} $). For the magnetic field we use large scale galactic magnetic field models based on Faraday rotation measurements and we have also studied the survival probability of photons in the Galactic plane.